Sew together 12 of these 30 degree triangles to create a complete circle; 6 to create a half-circle; or 3 to create a quarter-circle. Create Fans, Dresden Plates, etc. up to a finished size of 38 inches. Use the vertical lines to fussy cut stripes or cut half triangles (the 1/4 inch seam allowance is marked). Or cut 30; 45; and 60 degree units with the angles marked on the ruler.